1. Field of the Invention
The present invention relates to a detecting element for detecting a metal pipe before or after it is installed in or on the ground or detecting a body such as a crushing powder, explosive and the like loaded at a predetermined place and to a detecting apparatus using the detecting element.
2. Description of the Related Art
Many kinds of metal pipes having almost the same outside diameter are installed in and on the ground in large Sophisticated plants such as petroleum refining plants, electric power plants, ship yards, chemical plants and the like. When many kinds of metal pipes must be installed at a time so that these large plants are newly constructed in a short period of time, identification codes and characters are conventionally applied to the metal pipes themselves with coloring materials such as paints and the like which are difficult to be decolorized before the metal pipes are connected in order to prevent different kinds of metal pipes from being connected to each other. Then, the installation dates of the metal pipes, the materials of the metal pipes, the sizes of them, the manufacture of them, the names of fluids flowing in the pipes, piping systems of them and other necessary data are written on different drawings and papers or recorded in a computer as electronic data using the identification codes and characters as reference data. When the metal pipes are connected, the identification codes and the like of the metal pipes themselves are visually checked against the drawings, the papers and a computer list for the discrimination thereof. Further, when the metal pipes are inspected, repaired or replaced after they are installed, the identification codes and the like of the metal pipes themselves are visually checked against the drawings and the like for the discrimination thereof so that the metal pipes are checked against their history information in the same manner as that they are installed. Furthermore, the information of the result of inspection and the like of the pipes are recorded on the papers and the like while checked with the identification codes and the like of the metal pipes themselves.
In contrast, these metal pipe identifying and checking jobs are also carried out to various kinds of pipes buried in the ground such as gas pipes, tap water pipes, sewerage pipes, cable pipes, optical fiber pipes, oil transportation pipes, chemicals transportation pipes and the like, similarly. That is, buried metal pipes may be repaired or replaced after they are used for a long period of time. In a construction work carried out at the time, the positions of the buried metal pipes must be accurately located from the ground and earth and sand must be dug. Conventionally, metal pipe detecting markers are known as a device for detecting buried metal pipes. The marker is composed of a columnar ferrite, an antenna coil wound around the ferrite and a capacitor connected to both the ends of the antenna coil. The antenna coil and the capacitor constitutes a resonance circuit. The ferrite, the antenna coil and the capacitor are accommodated in an insulating case. The metal pipe detecting marker is buried at the necessary position of the metal pipe together therewith. Thereafter, the position of the metal pipe is detected by detecting the marker by resonating the resonance circuit from the ground by transmitting a radio wave having a specific frequency using a dedicated detecting apparatus and receiving the resonated radio wave in a construction work.
When a pipe is made of metal, in particular, when the pipe is a magnetic body such as a cast iron pipe, a steel pipe and the like, if the metal pipe detecting marker is directly mounted on the outer surface of the metal body or disposed at a position very near thereto, the resonance frequency of the resonance circuit of the marker is varied by the change of the self-inductance of the resonance circuit as well as the Q value of the coil is greatly lowered. Thus, the marker cannot be accurately detected. To cope with this problem, when the marker is used to detect the metal pipe, it is buried at a position spaced apart from the pipe by a distance larger than the diameter of the pipe.
However, in the conventional method of applying the identification code and the characters to the metal pipe itself and visually discriminating and checking them, a problem arises in that a considerable time and labor are necessary to discriminate and check metal pipes when they are installed under the ground where illumination facilities are not sufficiently provided, when they are installed in the ground or when they are installed on the ground in a complicated fashion, they may be erroneously identified.
To improve the above point, it is tried to mount a non-contact type RFID (radio frequency identification device) on a metal pipe. However, when the metal pipe is the magnetic body such as the cast iron pipe, the steel pipe and the like, if the RFID is directly mounted on the outer surface of the pipe body or disposed at a position very near thereto, the resonance frequency of the radio wave transmitted from an external identification device is varied by the change of the self-inductance of the antenna coil of the RFID as well as the Q value of the antenna coil is greatly lowered. Thus, there arises a problem that the function of the RFID cannot be achieved.
Further, when the markers are buried at positions spaced apart from metal pipes, the positions where the markers are buried and the axial lines of the coils of the markers are varied depending upon workers and a detection error may be increased. Further, when another construction work is carried out after a metal pipe is buried, the marker may be broken or the marker itself may be moved. Accordingly, there is also a disadvantage that the above conventional metal pipe detecting marker cannot detect a metal pipe in such a case.
Further, when a body to be detected is a crushing powder or explosive loaded in a hole drilled in a rock, rock bed, concrete and the like for crushing the rock and the like, it is necessary to accurately detect or search a crushing powder or explosive which remains without being exploded to secure the safety of a job for removing muck such as earth, sands and rocks after the crushing powder or explosive is exploded.
A first object of the present invention is to provide a body detecting element capable of accurately identifying a body without changing the resonance frequency of the radio wave transmitted from an identification device for activating a RFID circuit and without changing the Q value of an antenna coil even if the body detecting element is mounted on a body such as a metal pipe and the like installed in or on the ground integrally therewith and to provide a detecting apparatus using the detecting element.
A second object is to provide a body detecting element which is not almost broken and moved even if a body other than a body to be detected is dug up and to provide a detecting apparatus using the detecting element.
A third object of the present invention is to provide a body detecting element capable of accurately detecting a body such as a crushing powder or explosive which is loaded at a predetermined position and is not yet exploded and to provide a detecting apparatus using the detecting element.
A first aspect of the invention discloses a body detecting element which is buried in the ground together with a body and includes a magnetic member acting as a magnetic core, an antenna coil wound around the magnetic member and a capacitor or a piezo-resonator connected to both the ends of the antenna coil for forming a resonance circuit together with the antenna coil. In the detecting element, the body is a metal body and the antenna coil is mounted on the body integrally therewith with the outer peripheral surface thereof confronting the outer surface of the body.
When the antenna coil is mounted on the body such that the outer peripheral surface thereof confronts the outer surface of the body, the resonance circuit composed of the coil and the capacitor or the piezo-resonator is resonated and the lines of magnetic forces emitted from the resonance circuit are directed in the axial direction of the magnetic member. This direction is substantially in parallel with the outer surface of the body and many of the lines of magnetic force do not pass through the body. Thus, even if the body is composed of a ferromagnetic body such as cast iron, steel and the like, it is difficult for the body to be affected by the lines of magnetic force. As a result, since the self-inductance of the coil is less changed, the resonance frequency of the resonance circuit is scarcely changed. Further, since the Q value of the coil is little dropped, the width of resonance of the resonance frequency is made acute, whereby the resonance characteristics of the detecting element can be enhanced. At the time, when the piezo-resonator is connected to both the ends of the antenna coil, the change of the resonance frequency is reduced even if the self-inductance of the coil is somewhat changed.
In particular, when an electromagnetic shield member composed of copper, copper alloy or aluminum is interposed between the outer peripheral surface of the coil and the outer surface of the body as shown in a modification of the first aspect of the invention, the lines of magnetic force emitted from the resonance circuit scarcely passes through the body, whereby the resonance characteristics of the marker is more enhanced.
According to a modification of the first aspect of the invention, the body is a metal pipe, the magnetic member, the antenna coil and the capacitor or the piezo-resonator are wrapped with an insulating member, and the portion of the insulating member, which is in contact with the metal pipe, is formed in a recessed surface.
The formation of the portion of the insulating member in contact with the metal pipe in the recessed surface permits the detecting element to be stably mounted.
According to a modification of the first aspect of the invention, the body is a metal pipe, the magnetic member, the antenna coil, the capacitor or the piezo-resonator and the electromagnetic shield member are wrapped with an insulating member, and the portion of the insulating member for covering the electromagnetic shield member is formed in a recessed surface.
When the electromagnetic shield member is used, the formation of the surface of the insulating member on which the electromagnetic shield member exists in the recessed surface prevents the detecting element from being erroneously mounted.
A second aspect of the invention discloses a body detecting element which is buried in the ground together with a body and includes a magnetic member acting as a magnetic core, an antenna coil wound around the magnetic member and a capacitor or a piezo-resonator connected to both the ends of the antenna coil for forming a resonance circuit together with the antenna coil. In the detecting element, the body is a metal pipe composed of a non-magnetic material, and the magnetic member is formed to cover the outer peripheral surface of the metal pipe and mounted on the metal pipe integrally therewith.
When the resonance circuit is arranged such that the outer surface of the metal pipe composed of the non-magnetic material is covered with the magnetic member and the antenna coil is wound around the magnetic member, the diameter of the coil can be increased, whereby the detecting element having a high resonance performance can be obtained. The lines of magnetic force emitted from the resonance circuit being resonated are not affected by the metal pipe because the surface of the metal pipe acts as an electromagnetic shield member.
When the body is a metal pipe composed of a magnetic material as shown in a third aspect of the invention, if the magnetic member is formed so as to cover the outer peripheral surface of the metal pipe as the body through the electromagnetic shield member composed of copper, copper alloy or aluminum, the lines of magnetic force emitted from the resonance circuit being resonated are directed in the axial direction of the magnetic member which is substantially in parallel with the outer peripheral surface of the body. As a result, even if the body is composed of a ferromagnetic body such as cast iron, steel and the like, the electromagnetic shield member makes it difficult for the lines of magnetic force to be affected by the body.
According to a fourth aspect of the invention, the body is a crushing powder or an explosive and the magnetic member acting as the magnetic core is formed of a composite material containing Fe or Fexe2x80x94Co alloy powder or flake in an amount not less than 74 wt % to not more than 86 wt % and plastic in an amount not less than 14 wt % to not more than 26 wt %.
When Fe or Fe alloy is in an amount less than 74 wt %, it is difficult to obtain sufficient magnetic characteristics, whereas when it is in an amount exceeding 86 wt %, the magnetic member is made brittle. Further, to obtain a magnetic core composed of a columnar body from the magnetic member, it is preferable to make the cross-sectional shape of the columnar body to a rectangular shape or an elliptic shape to lower the resistance loss of the antenna coil, and it is further preferable that the ratio of the long side to the short side of the rectangular shape and the ratio of the major axis to the minor axis of the elliptic shape are not less than 1.2 to less than 16, respectively. When these ratios are less than 1.2 or not less than 16, the resistance loss of the antenna coil will be increased.
According to a fifth aspect of the invention, a detecting apparatus comprises a transmitting unit for transmitting a radio wave having a specific frequency from the ground to a body detecting element buried in the ground together with a body to resonate the resonance circuit of the body detecting element, a receiving unit for receiving a radio wave generated by the resonation of the resonance circuit of the detecting element, and a detection and display unit for detecting and displaying the received radio wave.
When a radio wave of specific frequency is transmitted from the transmitting unit of the detecting apparatus, the resonance circuit of the detecting element is resonated thereby and emits a second radio wave. The accurate position of the detecting element can be detected by the receiving unit which receives the secondary radio wave. As a result, the body can be reliably detected.
A sixth aspect of the invention discloses a body detecting element which is mounted on a body composed of a metal body and includes a magnetic member acting as a magnetic core, an antenna coil wound around the magnetic member and an RFID circuit connected to the antenna coil. The RFID circuit includes a memory for storing data characteristic to the metal body, is activated by a radio wave having a specific frequency and transmitted from a detecting apparatus, reads data from the memory in response to a read command issued by the data communication through the radio wave, writes data to the memory in response to a write command and issues a response command to the detecting apparatus. In the detecting element, the antenna coil is mounted on the body integrally therewith with the outer peripheral surface thereof confronting the outer surface of the body.
The external detecting apparatus transmits the identification code query signal of the detecting element thereto. When the antenna coil receives the radio wave of specific frequency of the query signal, the RFID circuit is activated by the power generated to the coil through the electromagnetic induction thereof. The detecting element having received the query signal transmits the identification code characteristic to the metal body to the detecting apparatus. The detecting apparatus having received the identification code specifies the body composed of the metal body. Since the detecting element is mounted on the body such that the outer peripheral surface of the antenna coil confronts the outer surface of the body, the lines of electromagnetic force generated to the coil and emitted therefrom are directed in the axial direction of the magnetic member. The direction is substantially in parallel with the outer surface of the body and many of the lines of magnetic force do not pass through the body. Thus, even if the body is composed of a ferromagnetic body such as cast iron, steel and the like, it is difficult for the lines of magnetic force to be affected by the body. As a result, since the self-inductance of the coil is less changed, the frequency of the query signal is scarcely changed. Further, since the Q value of the coil is little dropped, the detecting element is reliably activated as well as data communication can be carried out to the detecting apparatus.
In particular, when the electromagnetic shield member composed of copper, copper alloy or aluminum is interposed between the outer peripheral surface of the coil and the outer surface of the body, the lines of magnetic force emitted from the coil are scarcely pass through the body, whereby the identification performance of the detecting element can be more enhanced.
According to a modification of the sixth aspect of the invention, the body is a metal pipe, the magnetic member, the antenna coil and the RFID circuit are wrapped with an insulating member, and the portion of the insulating member, which is in contact with the body, is formed in a recessed surface.
The formation of the insulating member in contact with the metal pipe in the recessed surface permits the detecting element to be stably mounted.
According to a modification of the sixth aspect of the invention, the body is a metal pipe, the magnetic member, the antenna coil, the RFID circuit and the electromagnetic shield member are wrapped with an insulating member, and the portion of the insulating member for covering the electromagnetic shield member is formed in a recessed surface.
When the electromagnetic shield member is used, the formation of the surface of the insulating member on which the electromagnetic shield member exists in the recessed surface prevents the detecting element from being erroneously mounted.
According to a seventh aspect of the invention, a body detecting element is mounted on a body and includes a magnetic member acting as a magnetic core, an antenna coil wound around the magnetic member and an RFID circuit connected to the antenna coil. The RFID circuit includes a memory for storing data characteristic to the body, is activated by a radio wave having a specific frequency and transmitted from a detecting apparatus, reads data from the memory in response to a read command issued by the data communication of the radio wave, writes data to the memory in response to a write command and issues a response command to the detecting apparatus. The arrangement of the detecting element is characterized in that the body is a metal pipe composed of a non-magnetic material and the magnetic member is formed to cover the outer peripheral surface of the body and mounted on the body integrally therewith.
When the outer surface of the body composed of the non-magnetic material is covered with the magnetic member and the antenna coil is wound around the magnetic member, the diameter of the coil can be increased, whereby a detecting element of high performance can be obtained. The lines of electromagnetic force emitted from the antenna coil in response to the radio wave transmitted from the detecting apparatus are not affected by the metal pipe as the body because the surface of the metal pipe acts as the electromagnetic shield member.
When the body is a metal pipe composed of a magnetic material as shown in an eighth aspect of the invention, if the magnetic member is formed to cover the outer peripheral surface of the body through an electromagnetic shield member composed of copper, copper alloy or aluminum, the lines of magnetic force emitted from the antenna coil in response to the radio wave transmitted from the detecting apparatus is directed in the axial direction of the magnetic member which is substantially in parallel with the outer peripheral surface of the body. As a result, even if the body is composed of a ferromagnetic body such as cast iron, steel and the like, the electromagnetic shield member makes it difficult for the lines of magnetic force to be affected by the body.
According to a ninth aspect of the invention, a body detecting apparatus comprises a means for transmitting a radio wave having a specific frequency to a body detecting element mounted on a body integrally therewith, a means for activating the RFID circuit of the body detecting element in response to the radio wave, a means for reading and writing data from and in the memory of the RFID circuit, and a means for receiving a response signal from the detecting element, thereby identifying the body.
When the external detecting apparatus transmits a radio wave of specific frequency, the RFID circuit of the detecting element is activated by the radio wave and at the same time data is read and written from and in the memory of the RFID circuit. The body can be identified by the detecting apparatus having received a response signal from the detecting element.